Could the solution to global warming be as simple as a switch of cities?

For those who think the Kyoto Protocol is not working to cut greenhouse gas emissions that are heating the planet, why not take some lessons from the Montreal Protocol, praised as the world's most successful climate treaty?

Both the UN and the Bush administration plan to try out this idea this week as parties to the treaty gather in Montreal, 20 years after the pact to cut ozone-depleting chemicals was signed.

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The Montreal Protocol aims to cut down on emissions of chemicals that deplete the stratospheric ozone layer, which shields earth from ultraviolet solar radiation that can cause skin cancer and other ailments.

The ozone layer is still thin in spots, especially over the south pole, but the treaty is considered a raging success because it mapped a way to cut production of ozone-depleting substances.

So far, 191 countries from the developed and developing world have signed this pact, and have phased out more than 95% of ozone-depleting substances.

Because some chemicals that eat stratospheric ozone also contribute to global warming, the UN Environment Programme and the White House plan to urge speeding up some requirements of the Montreal Protocol.

They argue that this would have a bigger impact on climate change than the Kyoto Protocol, signed in Japan in 1997.

"We will push for an agreement among the parties to accelerate the phase-out of hydrochlorofluorocarbons (HCFCs), chemicals that not only destroy the ozone layer, but contribute significantly to climate change," the US State Department said in a statement before the meeting.

Faster phase-out

James Connaughton, head of the White House Council on Environmental Quality, says Washington wants HCFCs, used in refrigerators and air conditioners, phased out 10 years earlier than under the current timetable.

"It would produce at least two times the reductions [in greenhouse gases] than the Kyoto Protocol," Connaughton says.

The US and Australia are not part of the Kyoto Protocol, arguing that it would cost jobs and wrongly exclude developing nations like China and India from goals to cut their greenhouse gas emissions.

But using the Montreal Protocol to fight global warming is "simplistic", says one Washington-based environmental expert who deals with the US government.

Climate change is a more complex problem than ozone depletion, this consultant says, requesting anonymity.

And the big problem with climate change remains CO2 emissions, not ozone-depleting chemicals, the consultant says.

All the industries covered by the Montreal Protocol account for perhaps 5% of total global warming emissions, the consultant says, while CO2 from energy production and mobile sources accounts for 75%.

Annie Petsonk of the US-based non-profit consultancy Environmental Defense notes a fundamental difference between the Montreal and Kyoto treaties.

In the ozone pact, all countries are compelled to cut back on the amount of ozone-eating substances they produce. But developing countries have a 10-year grace period and get financial incentives to do it.

Under the Kyoto Protocol, developing countries are exempt from limiting emissions from greenhouse gases, Petsonk says.

Drusilla Hufford, director of stratospheric protection at the US Environmental Protection Agency, says some part of the Montreal Protocol's success was its genesis: based on science and flexible in the way its goals could be met.

It also had the support of the US administration, which is not the case with the Kyoto agreement on climate change.

In summary, CFCs and their HCFC replacements trap heat, but make far less of a contribution to atmospheric warming than CO2.

Ozone itself also traps heat, albeit via a different mechanism to CO2.

Near the ground, ozone is formed from air pollutants and traps heat. In the stratosphere, ozone heats the surrounding air when it is photo-dissociated by solar ultraviolet photons, but cools the surrounding air when it radiates infrared energy to space.

The heating effect, which occurs only in daylight, is more effective than the cooling effect, which occurs day and night.